Integral beam lamp and projection system



March 6, 1962 G. LESSMAN INTEGRAL BEAM LAMP AND PROJECTION SYSTEM FiledMarch 21, 1958 a M 5 u United States Patent 3,023,667 INTEGRAL BEAMLANIP AND PROJECTION SYSTEM Gerhard Lessman, Rutland Township, KaneCounty, 111., assignor to Bell & Howell Company, Chicago, Ill., acorporation of Illinois Filed Mar. 21, 1958, Ser. No. 723,046 7 Claims.(Cl. 88-24) This invention relates to integral beam projection lamps formotion picture and similar projectors, and to a projection systememploying same. By integral beam projection lamps is meant the class oflamps in which a reflector optical system, replacing the conventionalglass condenser lenses, is an integral part of the lamp structure. Sucha lamp may be in the form of a so-called sealed beam lamp, of whichautomobile headlamps are an example, or it may be similar toconventional tubular bulb projection lamps, but with a reflector mountedinternally upon suitable supports, which is the form that has beenselected for illustrative purposes.

It is generally known that the luminous efliciency of incandescent lampsis greater at low design voltage operation. For this reason it isdesirable to operate integral beam projection lamps at less than linevoltage which is normally about 115 volts. The operation of integralbeam projection lamps at less than standard voltage presents a powersupply problem in motion picture and similar projectors if the cost ofthe transformer or choke necessary to reduce from line to lamp voltageis not permissible for the application. An obvious solution, oftensuggested, is to connect an auxiliary resistor in series with the lampcoil to reduce the voltage applied thereto. Unfortunately, this is anitem of expense for a resistor capable of handling the large wattageinvolved. The necessary wiring and mountings add further to the cost.More important are the energy losses in theresistor. Using such a systemthe advantages of low wattage and high efliciency in the integral beamlamp are thrown away, to the end that almost as much power is used as inconventional biplane projection lamps. Inasmuch as most motion pictureprojectors and slide projectors use shaded pole motors for driving theprojection mechanism and the cooling fan or blower, it has been foundfeasible to use the motor field winding as a choke in series with thecoil of the low voltage lamp. Naturally, the design of the field windingis then adjusted to provide the required ampere turns at the correctlamp current. A great advantage of the motor field winding used as achoke is the fact that no cost is added, because the amount of copperrequired for the same number of ampere turns is approximately the sameunder most conditions. Thus the choke is much superior economically to atransformer secondary winding added to the motor field, which has alsobeen proposed.

However, especially in motion picture projectors, it is often necessaryor desirable to be able to operate the motor without at the same timeburning the projection lamp in series therewith, for this wouldunnecessarily shorten the useful life of the relatively short livedprojection lamp. A typical occasion for this requirement would be duringthe rewinding of motion picture film. It is of course possible to devisecircuitry for switching a resistor equal to the lamp resistance in placeof the lamp during the rewind cycle. This would require the use of afairly high wattage resistor, mounted in the cooling air stream foradequate heat dissipation. The cost of the resistor, the wiring, andnecessary fastenings is in many instances greater than is economicallyjustifiable by the illumination gains attributable to the low voltagelamp design.

I have devised an arrangement wherein no additional 3,023,667 PatentedMar. 6, 1962 external resistor is required, but a resistor in the formof a second tungsten coil is incorporated within the integral beam lampstructure. The advantages of such an arrangement are the convenience ofwiring because the lamp is fitted with a four pin base suitable formaking connections to the integral resistor, the absence of a coolingproblem because the lamp is inherently capable of dissipating the heatdue to the second resistor which is of the same wattage as the lampcoil, and the essentially lower cost of the internal lamp resistorcompared to an external resistor of equal wattage dissipation. Furtheradvantages will appear upon a reading of the following specification.

In order to describe the invention in detail, reference is made to theappended drawings, in which:

FEGURE l is a pictorial view of a currently available integral beamprojection lamp; and

FIGURE 2 is a schematic wiring diagram of a typical lamp application ascontemplated in this invention.

The drawings and the following description are of a single illustrativeembodiment of my invention, which may be practiced with variations fromthe embodiment described without departing from the spirit of theinvention.

Referring now to FIGURE 1 of the drawing, it will be observed that thereference character 10 designates, generally, an integral beam lampwhich includes a sealed glass envelope or bulb 11 onto a four pin waferstem type base 12, known to the trade as a True Focus base. The glassenvelope or bulb 11 has mounted therein a horizontally coiled tungstenlamp filament or coil 14 which may be of about watts rating and arrangedto operate at a voltage less than standard line voltage or at a voltagewhich may be of the order 45 volts. The lamp filament or coil 14 islocated at one of the foci an elliptical reflector 15 which is focusedupon a projector aperture (not shown) that is located at the other fociof the reflector 15. The reflector 15 is supported at the bottom by wirestems 16 and 17 which extend outwardly through the base 12 and provideat their lower ends front pins 18 and 19. It will be understood that thefront pins 18 and 19 constitute two of the four pins of the base 12. Theelliptical reflector 15 is centrally supported also by ceramic grommets29 which are sleeved over filament coil lead wires 21 and 22 that extendthrough the reflector 15 and are attached to and held by wire stems 23and 34, respectively. The wire stems 23 and 24 extend downwardly throughthe base 12 and terminate in rear pins 25 and 26 which constitute theother two pins of the four pin base. A central key pin 27 is employedfor properly orienting the base 12 in the cooperating socket.

It will be observed that the front pins 18 and 19 are normallyelectrically connected together through the metallic ellipticalreflector 15. However, they are in sulated from the rear pins 25 and 26across which the lamp filament or coil 14 is connected. In accordancewith this invention advantage is taken of the fact that the front pins18 and 19 are insulated from the rear pins 25 and 26 to connect atungsten coil or internal resistor '30 between the wire stem 23 and thewire stem 17 or between the pins 25 and 19. Preferably the tungsten coilor internal resistor 30 has a voltage and wattage rating substantiallyequal to or near that of the lamp filament or coil 14. Since the wirestems 1'6 and 17 are interconnected, the tungsten coil or internalresistor 30 can be connected to either of them.

As will appear hereinafter the only function of the tungsten coil orinternal resistor 30 is to provide a resistance in a circuit equivalentto that of the lamp filament or coil 14. The tungsten coil or internalresistor 30 then can be positioned at the lower part of the glassenvelope or bulb 11. Preferably it is positioned, as

shown, below the lower edge of the reflector 15 where danger of itsbeing short circuited is avoided and yet it is out of sight of theoptical system. However, it is located at a safe distance above thewafer stem base 12.

While the lamp filament or coil 14 must be designed in accordance withgood lamp design practice for this type of projection lamp in terms ofsource size, type of winding, and rated life, it is unnecessary toimpose equally stringent requirements upon the tungsten coil or internalresistor 30 since, as pointed out, it functions only as a resistor andnot as a light source. Any convenient coil configuration can be used forthe tungsten coil or internal'resistor 30 which approximates theelectrical characteristics of the lamp filament or coil 14. In generalthe tungsten coil or internal resistor 30 can be designed for a loweroperating temperature than that of the lamp filament or coil 14 so as toassure a long, safe operating "life. When a lower operating temperatureis used for the tungsten coil or internal resistor 30, there is asmaller amount of blackening of the glass envelope or bulb since lesstungsten is evaporated from the tungsten coil or internal resistor 30 atsuch lower temperature.

FIGURE 2 shows one application for the integral beam lamp provided withthe tungsten coil or internal resistor 30. The circuit here shown can beemployed in a projector for operating the projector in the usual mannerand for operating the rewind mechanism at which time it is not desiredthat the lamp filament or coil 14 be energized in order to prolong itslife.

In FIGURE 2 it will be observed that the integral beam lamp 10 is showndiagrammatically with the lamp filament or coil 14 being connectedbetween the rear pins 25 and 26, the tungsten coil or internal resistor30 being connected between the rear pin 25 and the front pin 19, and thefront pins 18 and 19 interconnected. The common connection between thefront pins 18 and 19 is provided,-as described above, by the metallicreflector 15.

The motor for operating the projector and rewind -mechanism .isillustrated, generally, at 31. It includes a rotor 32 which can beconnected selectively to drive either the projector or the rewindmechanism, the arrangement being such that for either operation therotor 32 rotates in the same direction. Cooperating with the rotor 32 isa magnetic core 33 that is provided with a field winding 34. Inaccordance with this invention the vfield winding 34 is connected in.series circuit relation with either the lamp filament or coil 14 or thetungsten .coil or internal resistor 30.

The system shown in FIGURE 2 can be energized from a suitable source ofalternating current such as 115 volt source as indicated as constitutingthe line, A conductor 35 directly connects one terminal of the fieldwinding 34 :to the line. Another conductor 36 connects the otherterminal of the field winding 34 to the rear pin 25 which is a commonconnection to the lamp filament or coil 14 and to the tungsten coil orinternal resistor 30.

For operation as a projector the lamp filament or coil 14 is energizedin series with the field winding 34. The circuit is completed throughconductor 37, switch blade 38 and conductor 39 to the other side of theline.

When it is desired to operate the motor 31 for rewinding purposes and itis not desired to energize the lamp filament or coil 14, the switchblade 38 can be shifted to the alternate position where the circuit tothe tungsten coil or internal resistor 30 is completed through acondoctor 40.

From the foregoing description it will be apparent that the fieldwinding 34 of the motor 31 has connected in series therewith thenecessary amount of resistance when the system is operated either forprojection purposes or for rewinding purposes. It is merely necessary toshift the switch blade 38 from one position to the other to effect oneor the other type of operation. The intermediate position of the switchblade 38 can be used a n of p i ion, if desired.

While for the sake of explicitness I have described a specificembodiment of my invention, I do not wish to be limited thereby but only-by the scope of the following claims.

What is claimed as new is:

1. In a motion picture projection system capable of selective projectionand film rewinding operations, in combination, a source of line voltage,a projection lamp having a sealed bulb containing a lamp filament and aninternal resistor coil of approximately the same electricalcharacteristics, a projector motor having a field winding, and circuitmeans including switch means for selectively connecting said fieldwinding for energization across said source through said lamp filamentwhen said projector is being used for projecting and through saidresistor coil when said motor is being used for rewinding.

2. In a motion picture projection system capable of selective projectionand film rewinding operations, in combination, a source of line voltage,a projection lamp having a sealed bulb containing a lamp filament and aninternal resistor coil of approximately the same electricalcharacteristics commonly connected together, a projector motor having afield winding, and circuit means including switch means for selectivelyconnecting said lamp filament to said field winding in series circuitrelation for energization across said source when said projector motoris being used for projecting, and said resistor coil when said projectormotor is being used for rewinding.

3. In a motion picture projection system capable of selective projectionand film rewinding operations, in combination, a source of line voltage,a projection lamp having a sealed bulb containing a lamp filament and aninternal resistor coil of approximately the same electricalcharacteristics, a projector motor having a field winding, and circuitmeans including switch mean for selectively connecting said fieldwinding to the common connection between said lamp filament and saidresistor coil and for energization across said source through theconnected one of said filament and coil whereby the lamp filament willbe energized when the projector motor is being used for projecting andthe resistor coil will be energized when said motor is being used forrewinding.

4. In a motion picture projection system capable of selective projectionand film rewinding operations, in combination, a source of line voltage,a projection lamp having a bulb sealed to a base through which at leastthree Wire stems project externally in insulated spaced relation, a lampfilament and a resistor coil in said bulb commonly connected to one ofsaid wire stems and individually connected to the other two stems, aprojector motor having a field winding, and circuit means includingswitch means for selectively connecting through said wire stem said lampfilament and said resistor coil to said field winding in series circuitrelation for energization across said source whereby said lamp filamentwill be energized when the projector motor is being used for projectingand the resistor coil will be energized when said motor is being usedfor rewinding.

5. In a motion picture projection system capable of selective projectionand film rewinding operations, in combination, a .source of .linevoltage, a projection lamp having a bulb sealed to a base through whichat least three wire stems project externally in insulated spacedrelation, a lamp filament and a resistor coil in said bulb commonlyconnected to one of said wire stems and individually connected to theother two stems, a reflector mounted on one of said stems for opticalcooperation with said lamp filament and having its reflecting surfaceout of the line of sight of said resistor coil, a projector motor havinga field winding, and circuit means including switch means vforselectively connecting through said wire stem said filament and .saidcoil to said field winding in series circuit relation for energizationacross said source whereby said lamp filament will be energized when theprojector motor is being used for projecting and the resistor coil willbe energized when said motor is being used for rewinding.

6. In an integral beam projection lamp of the class described, incombination, a bulb sealed to a multiple pin base, a reflector withinsaid bulb, a lamp filament within said bulb within the field of view ofsaid reflector, a resistor coil of approximately the same resistance asthat of said lamp filament within said bulb and out of the field of viewof said reflector and out of the optical system of the lamp and circuitmeans for separately energizing said filament and coil through saidmultiple pin base.

7. In an integral beam projection lamp of the class described, incombination, a bulb sealed to a multiple pin base, a stemmed lampfilament within said bulb supported by and energized through a pair ofthe pins of said base, a stemmed reflector for said lamp filamentsupported by 6 at least another pin of said base, and a resistor coilwithin said bulb out of the optical field of said reflector and out ofthe optical system of the lamp and connected and supported at one end byone of the stems of said lamp filament and at the other end by the stemof said reflector.

References Cited in the file of this patent UNITED STATES PATENTS1,596,481 Debrie Aug. 17, 1926 1,646,442 Brizendine Oct. 25, 19271,651,431 Wood Dec. 6, 1927 2,196,738 Nagel Apr. 9, 1940 2,481,694Schubert et a1. Sept. 13, 1949 FOREIGN PATENTS 170,943 Switzerland Oct.16, 1934

